Lens grinding machine and method



July 24, 1956 Q E EVANS 2,755,602

LENS GRINDING MACHINE AND METHOD Filed Dec. 17, 1951 5 Sheets-Sheet 1INVENTOR. Char/e5 5. 51/4125 ATTORNEY.

y 4, 1956 c. E. EVANS 2,755,602

LENS GRINDING MACHINE AND METHOD Filed Dec. 17, 1951 5 Sheets-Sheet 2INVENTOR.

Char/es E. EI/QZZS July 24, 1956 c. E. EVANS 2,755,602

LENS GRINDING MACHINE AND METHOD Filed Dec. 17, 1951 5 Sheets-Sheet 5INVENTOR.

war/es 5 51 4225 y 4. 1956 c. EVANS 2,755,602

LENS GRINDING MACHINE AND METHOD Filed Dec. 17, 1951 5 Sheets-Sheet 4 fa :3 e

IN VEN TOR.

M. TTORNEY.

y f July 24, 1.956 c. E. EVANS 2,755,602

LENS GRINDING MACHINE AND METHOD Filed Dec. 17, 1951 s Sheets-Sheet 5 UT La l I I P 45 1 I l I .w'w 43 I I l l l INVENTOR. Char/ea E. Ems

- 'ITORNEY.

United States Patent LENS GRINDING MACHINE AND METHOD Charles E. Evans,Naperville, Ill. Application December 17, 1951, Serial No. 262,068

23 Claims. (Cl. 51120) This invention relates to grinding machines forspectacle lenses and other objects and to spectacle lenses producedthereby.

It is an object of the present invention to provide an improved grindingmachine adapted for producing surfaces of varying curvature.

It is a further object of the present invention to provide an improvedspectacle lens.

In my Patent No. 2,109,474 issued March 1, 1938, and entitled SpectacleLens, I disclosed a lens having a graduated focal grinding which mergedat either or both edges with spherical grindings for distance and, or,reading vision, so that the eye might be shifted from registration withone portion of the lens to another without experiencing anydiscontinuity or unevenness in vision. Heretofore, however, such a lenshas had to be produced in several distinct grinding operations.

It is, therefore, an object of the present invention to provide agrinding machine for producing in a single grinding operation a lenshaving portions of different curvature including at least one graduatedcurvature or curvature of gradually varying radius.

In my Patent No. 2,112,836 issued April 5, 1938, and entitled LensGrinding Machines, I disclosed a grinding machine for generating aninvolute curve by actually rolling a circular gear segment on a rack. Inthe present invention, however, an involute is simulated withoutactually rolling one part on another.

It is, therefore, another object of the present invention to provide agrinding machine for generating a'simulated involute curve.

It is still another object of the present invention to provide agrinding machine adapted for producing multifocal lenses includinggraduated focal surfaces, having improved side distant vision, sideintermediate vision, and near vision.

it is yet another object of the present invention to provide an improvedpolishing assembly for polishing lenses, including an improved polishingwheel and an improved lens mounting and guard for cooperation therewith.

It is still another and further object of the present invention toprovide an improved grinding wheel assembly adapted for use in the lensgrinding machine of the present invention.

Other objects, features and advantages of the present invention will beapparent from the following detailed description of several embodimentsof my invention taken in connection with the accompanying drawings, inwhich:

Figure 1 is a front elevational view, with certain parts broken away andothers in section, illustrating one embodiment of a grinding machineaccording to the present invention;

Figure 2 is a right side elevational view of the machine of Figure 1;

Figure 3 is a plan view of the machine of Figure 1;

Figure 4 is a fragmentary enlarged front elevational view of an upperportion of the machine of Figure 1,

2 showing the jig for guiding the object being ground in centralposition;

Figure 5 is a partial horizontal sectional view taken substantiallyalong the line aa in Figure 4;

Figure 6' is a fragmentary enlarged front elevational view of thegrinding jig of Figure 4, but showing the inner jig assembly pivotedaway from central position during grinding of a portion of constantdioptric curvature adjacent one edge of the object being ground;

Figure 7 is a vertical sectional view of a polishing assembly accordingto the present invention;

Figure 8 is an enlarged fragmentary front elevational view similar toFigure 4, but showing a modified form of grinding jig;

Figure9 is a diagrammatic view illustrating an improved lens producedwith the use of the grinding jigof Figure 8;

Figure 10 is a bottom plan view of the lens of Figure 9; and

Figure 11 is a plan view of a lens produced by the machine of Figure 1.

The embodiments of the grinding machine illustrated are adapted to grindportions of a surface of constant radius and portions of graduallyvarying radius, by way of example and not by way of limitation. Themachines are further illustrated as being employed for grindingspectacle lenses, but it is not the purpose to limit the invention tosuch lenses, since, for example, dies for use in molding plastic lensescould also be ground by the machine. I

Referring first to the embodiment of the invention illustrated inFigures 1 to 6 and particularly to Figure 1, a grinding jig A isutilized for guiding movement of a lens B or other object to be ground,in operative relation to a grinding wheel assembly C. The jig A includesan outer jig mechanism D for raising and lowering the lens B and aninner jig mechanism E for guiding the lens B in an oscillatoryfront-rear movement in a plane normal to the plane of Figure 1 and in alateral movement in the plane of Figure 1.

The jig and grinding wheel assembly are illustrated by way of exampleand not by way of limitation as being mounted vertically in an uprightframework including a lower generally rectangular frame 1 and a motorsupport 2. Motor 3 which is mounted on the support 2 drives the grindingwheel assembly C by means of grooved pulley 4 and belt 5 forming aclosed loop around idler pulley 6 on pulley shaft 7 mounted by brackets8, Figures 2 and 3, pulley 9 fixed to shaft 10, integral pulley 11 onthe bearing casting 12, Figure l, and idler pulleys 9 and 6', pulley 9'being journaled on shaft 10 and pulley 6 being journaled on shaft 7,Figure 3.

As seen in Figure 1, the bearing casting 12 is journaled on the fixedshaft 13, the lower end of which is rigidly held in the supporting block14 by means of clamping screw 15, the supporting block being fixed tothe lower frame 1. As the bearing casing 12 is rotated by means ofintegral pulley 11, the grinding wheel 16 is rotated on the axes of itsmounting shaft 17 by means of gear 18 on fixed shaft 13 and planetarygear 19 meshing therewith and mounted on the grinding wheel shaft 17.The grindin-gwheel also revolves about the fixed shaft 13 which is theaxis of rotation for the bearing casting 12.

In the base of the supporting block 14 is fitted an adjusting screw 1411which is supplied with a micrometerlike head 14b and a lock nut 140.This screw bears against the lower end of shaft 13 and supplies verticaladjustment for shaft 13 and the assembly mounted thereon includingbearing casting 12 and grinding disk 16, thus enabling accuratepositioning of the grinding disk.

It will be understood that the direction of travel of the grinding wheel16 is constantly changing with respect to the lens'surface, at the pointof contact between the two, and also this point of contact is constantlyshifting on the grinding wheel surface. This motion prevents groovingand scratching of the lens surface and tends to produce uniform wear onthe grinding wheel and to keep the same true.

As seen in Figure 1, the shaft 10 is journaled between bearing members21 and 22 which are supported by the lower frame 1, and is driven by thepulley 9 rigidly fixed thereon. Rotary motion of the shaft 10 isconverted into a reciprocating movement to furnish the motive power foroscillating the inner jig assembly E by a first moving means includingpinion 23 on shaft 10, gear 24 meshing therewith, rotatable shaft 25carrying gear 24 and journaled by hearing members 26, 27 and 28, Figure3, adjustable crank arm 29 rigidly fixed to rotatable shaft 25 adjacentbearing member 26, Figure 3, and rod 30, Figure 2 (extending generallyhorizontally above the uppermost run of pulley belt at the level ofshaft 25), rod 30 being connected at one end to crank arm 29 by means ofa ball and socket joint (not shown). The opposite end of the rod 30 isoperably fastened to lens block arm 31 by means of another ball andsocket connection 30, Figures 1, 4 and 6 (adjacent lens B). The innerjig assembly E is thus oscillated in a front-rear direction about thebearing block journals 72, 72 of outer jig assembly D to cause what maybe designated the width of the lens B to come into contact with thegrinding wheel 16 (the length or height of the lens being shown inFigure 1). The path of travel of said carrier in said front-reardirection is controlled by a first control means comprising the journals72 to produce an arcuate movement of said lens.

The inner jig assembly E is actuated by a pair of inner ratchetmechanisms 59 and 63 and the outer jig assembly D raises and lowers theinner jig assembly E by means of outer ratchet mechanisms 67 and 69,Figures 1 and 3. These ratchet mechanisms are driven by a cam member 32,Figure 3, rigidly fastened to the rotatable shaft 25. The cam member 32operates against a roller 33 rotatably mounted between lever arms 34 and35, Figure 1 (at the right), the lever arms being pivotally connected attheir lower ends to supporting bracket 36, rigidly fastened to the lowerframe 1. Between the upper ends of the lever arms 34, 35 is journaledone end of rod 37, Figures 2 and 3, which at the other end is pivotallyconnected to lever arm 38, Figure 3. It will be observed from Figure 2that the cam member 32 has a pair of opposed lobes 32' which uponrotation of the cam member will impart to the rod 37 an intermittentfore-aft reciprocal motion, the ratchets being actuated twice eachrevolution of cam member 32. Since the lever arm 38 is rigidly fixed toa vertically extending shaft 39, Figures 1 and 2, the reciprocal motionis converted into an intermittent rotary oscillation of the shaft 39,which is journaled in bearing brackets 40, 41, 42 mounted on the upperframe comprising spaced upright frame members 43.

For maintaining operative relation between the roller 33 and the cammember 32, Figure 2, a rod 44 is pivoted to the lever arm 38 and carriesa compression spring 45 which abuts at one end the lever arm 38 and isseated at the other end against an apertured plate 46, Figures 2 and 3,through which the rod 44 extends. For adjustably limiting the forwardmotion of the rod 44 under the urging of the spring 45 in returning theroller 33 toward the cam 32, a keeper nut 47 is threaded onto the freeend of the rod 44 for abutment with the plate 46 in inactive position ofthe rod. By adjusting the motion of the rod 44 by means of keeper nut47, the action of the ratchet mechanisms 59, 63, 67 and 69 can beregulated, thus controlling the rate of feed produced by the ratchetscrews 71, 71, 79 and S3.

The inner ratchet mechanisms 59 and 63 are adapted to be driven from thevertical shaft 39 by means of lever arms 48 and 49, Figure 2, which arerigidly fixed to the shaft 39 adjacent lower and intermediate bearingbrackets 41 and 42. The lever arms 48, 49 pivotally mount a verticallyextending slotted bar 50, Figure 1, to which is fixed in parallelrelation a solid bar 51. A horizontally extending rod 52 extends throughthe slotted bar 50 and bears against the solid bar 51, Figures 1 and 3.The rotary motion of the shaft 39 due to the cam member 32 thus impartsto the rod 52 a sidewise intermittent reciprocating movement, while thearrangement of the slotted bar 59 and solid bar 51 permits verticalmovement of the rod 52 relative to the bars during raising and loweringof the inner jig assembly E. The rod 52 extends through the right-handpivot shaft 75 of the inner jig assembly E so that the assembly is alsofree to oscillate in a fore-aft direction about shafts 75.

As best seen in Figure l, reciprocal motion of the rod 52 is transmittedto upright lever arm 53 which is rigidly fixed to rotatable shaft 54,pivotally supported by a movable support or carriage comprisinghorizontal side bars 56. As seen in Figure 3, the shaft 54 extendsrearwardly and has at its rear end a lever arm 57, Figure l, fixedthereto. The upper end of lever arm 57 is pivotally connected to theextension 58 of the lever arm of the reversible ratchet assembly 59which in turn is operably connected to the reversible ratchet assembly63 by means of removable bar 62 and rods 60 and 61. The rod 52 is keptin contact with the solid bar by means of wire spring 64 mounted onrotatable shaft 54 and bearing against lever arm 57 and side bars 56.

Thus the rotary oscillation of the shaft 39 due to the action of the cammember 32 is transmitted to the lever arms of the reversible ratchetassemblies 59 and 63. The ratchet assemblies 59 and 63 may consist ofsleeves (not shown) which are journaled in blocks 78 and 82, Figure 4,and are internally threaded to engage the screws 79 and 83. Fixed tothese sleeves are ratchet wheels 59a, 63a which are operated by means ofratchet pawls 59b and 63b, Figure 3, to drive the ratchets in eitherdirection as desired, or, as shown in Figure 3, to set the ratchets inneutral, the ratchets can operate even while the assembly E is beingraised and lowered and oscillated about pivot shafts 75.

The outer ratchet assemblies 67 and 69 are also actuated from therotatable shaft 39. As seen in Figure 3, a lever arm 65 is rigidly fixedto the shaft 39 at one end and is pivotally connected at the other endto the extension 66 of the reversible ratchet assembly 67. The extension66 is operatively connected by means of the rod 63 to the lever of thereversible ratchet assembly 69.

The ratchet assemblies 67 and 69 operate to raise and lower the innerjib mechanism B. As seen in Figure 2, blocks 70 which are bolted to thetops of spaced uprights 43 of the upper frame 43 journal the ratchetassemblies and have ratchet screws 71 extending downwardly therethroughto a rigid connection with the bearing blocks 72, Figure l, whichjournal the inner jig assembly E for fore-aft oscillation. The blocks 72are vertically slidable between vertically extending plates 73, Figures4 and 5, which are bolted to the upper frame uprights 43. The plates 73comprise normal movement mounting means mounting the carriage S6 forlinear movement generally normal to the grinding surface. The ratchets67 and 69 comprise bearing member moving means or carriage mov- 3 inneutral position. Rotation of the ratchet wheels 67a,.

arse-nos 69a rotates the ratchet sleeves in the'blocks'70 to raise orlower the ratchet screws 71.

As best seen in Figure 5, the inner jig assembly E is journaled incarriage mounting means comprising the bearing members or blocks 72 bymeans of spacer blocks 74 mounted between the side plates-56 andrigidlycarrying laterally projecting tubular pivot shafts 75. As willhereinafter be described, since the carrier for the lens'or other objectB is to be maintained at a substantially constant height above thegrinding wheel 16, Figure 1, the crank arm 29 and-rod 3%) connected tothe lens carrier arm 31 for oscillating the inner ji assembly E need notbe raised and lowered with the raising and lowering of the side plates56 and bearing blocks 72.

For cooperating with the inner ratchet mechanisms 59 and 63 in guidingthe carrier for the object to be ground in lateral movement in relationto-the grinding wheel 16, a pair of first outer plate members 77, Figure4, are pivotally mounted within the space between the side bars 56 onfirst member mounting means or first pivot means comprising pins 76,Figure 5. These plate members 77 have generally upwardly extending arms77 carrying therebetween spacer block 78 in which is journaled thereversible ratchet assembly 63, whose ratchet screw 79 extendsdownwardly between plate members 77 to a rigid connection with block 80which slides between plates 77.

Referring particularly to Figure 4, the ratchet assembly or first membermoving means 59 is operative to pivot 21 first member comprising platemembers 77 about pivots '76. The assembly is supported by plates81extending upwardly from between the side bars 56 to which plates 81are bolted. At the upper end of the plates 81, is fastened spacer block82 in which is journaled the ratchet assembly 59. The ratchet screw 83depends between the plates 81 and is rigidly connected at its'lower endwith block 84 which in turn slides between the plates 81. A thinmetalband 85. connects the block 84 with the spacer plate 86 fastenedbetween plates 77 for pivoting of the outer plates 77 about pins 76.

The other ratchet assembly or second or involute member or involutemoving means 63 is operative to control movement of a second or involutegenerating member comprising inner plate 38 which is pivotally fastenedto the plates 77 by a second or involute member or involute mountingmeans or second pivot means comprising a pin 39. The sliding block 8% ofthe ratchet assembly 63 is connected to the inner plate 88 by a means ofanother thin metal band 87. Thus vertical movement of ratchet screw 79pivots the inner plate 83 about pivot 89.

The inner and outer guidin plates '77 and 88 are biased downwardly inthe illustrated embodiment, by a counterweight 93, Figure l, which isconnected to inner plate 38 by means of hole 38 in the plate andflexible cable 90, the cable being guided by pulleys 91 and 92. Theweight 93 thus acts to overcome the frictional resistance of the slidingsurfaces and to take up the slack of the various parts and to hold theparts in proper position.

The lens or other object to be ground is carried by the inner plate 83on a carrier comprising the arm 31 connected to the lower end of theplate and a block 94 selectively spaced therefrom by means of shims 95and rigidly fastened to the arm 31 by means of screws. If a lens is tobe ground, the lens blank B is fastened to the lens block 94 by means ofa layer of pitch or some other suitable material indicateddiagrammatically at 96.

it will thus be seen that the inner jig assembly B may be reciprocatednormal to the grinding wheel surface by means of ratchet assemblies 67and 69 operated in conjunction, and that the entire inner jig assemblymay be oscillated about an axis parallel to the grinding wheel surface.It will further be clear that the ratchet assemblies 63 and 59, operatedseparately, will cause the carrier assembly or carrier Iii-94 to beselectively pivoted about one of two spaced pivots 89 and 76,respectively.

Operation The manner of operation of the jig assembly A shown in Figures4 and 6 will now be readily understood from the following description.

By way of example and not by way of limitation the grinding of aspectacle lens will be described, the lens to have a lower portion ofconstant dioptric power for use in reading, an upper portion of constantdioptric power for use in distance vision, and an intermediate portionof gradually varying dioptric power merging at the top and bottom withthe constant power portions of the lens.

With the inner jig assembly E in the position shown in Figure 6, whatmay be designated the top or upper portion of the lens blank B is incontact with the grinding wheel 16. The connector bar 62, Figure 4', hasbeen removed and the inner ratchet mechanism 59 has been actuated topivot the inner jig assembly E counterclockwise about the pivot 76 fromtheposition of Figure 4. The ratchet pawls are set in'neutral positionso that the ratchet mechanisms will all remain at rest.

To set the machine in motion, the motor 3 is started. The grinding wheel16 will now be rotating on its own axis and revolving in planetaryfashion about the fixed shaft 13, Figure 1. The entire inner jigassembly E will be oscillating fore and aft about the pivot shaft bymeans of a driving connection with the ball and socket joint 36 carriedby lens supporting arm 31, Figure 6.

This oscillating motion about pivots 75, 75 will bring what may betermed the width of the lens blank Binto contact with the grinding disk16, the blank will swing on a radius which is eifectively theperpendicular distance between the axis X-X of the pivots 75, 75 andthe'surface of the grinding wheel. This radius may be designated RX forconvenience. A circular arc of very narrow height is thus ground acrossthe width of the top portion of the lens blank, the are having aconstant radius RX. It will be observed that the pivot 76 is on the axisA-A, so that radius RX equals the distance from pivot '76 to the pointof contact of the lens blank with the surface of the grinding disk 16.

Lowering of the right-hand inner ratchet screw 83 by means of ratchetmechanism 59, for example at the end of the forward swing of the lensblank B about pivots 75, 75 and at the end of the rearward swing, willlower outer plates '77, and inner plate 88 therewith, clockwise aboutpivot 76 to grind successive narrow height circular arcs of radius RX.Since both crank 29 for oscillating the lens and cam member 32' foractuating the ratchet mechanisms are driven by the shaft 25, Figures 2and 3, it will be readily apparent that the ratchet 59 can besynchronized with the oscillation to lower the lens blank about pivot 76at each end of the swing of jig E on pivots 75.

It will be understood that since the lens is swung 1at erally aboutpivot 76 as well as being swung in the foreaft direction about pivot 76,a generally segmental spherical curvature of substantially constantradius is generated by the machine. The portion of the lens groundcorresponds in general location to the portion PQ in Figures 10 and 11,the radius RX corresponding to the distance between XI and the circulararc PQ in Figure 9.

If now it is desired to grind an intermediate portion of the lens with agradually varying radius, the intermediate portion corresponding ingeneral location to the portion Q, R, S, T in Figures 10 and 11, theleft hand inner ratchet 63 may be actuated to raise the inner'platemember ES to pivot the lens clockwise about pivot 89, Figure 4, theouter ratchets 67 and 69 being actuated in exact synchronism tocorrespondingly lower the entire inner jig assembly E. Since all theratchets are actuated from the same cam member 32, such synchronism isreadily obtained. The means for moving the'carrier into operativerelation with the grinding member, in-

cluding cam member 32 and inner ratchets 59 and 63 and outer ratchets 67and 69, will be termed the second moving means. The second moving meansmove the lens in a second direction transverse to the front-reardirection and the path of travel in said second direction is confined bymeans of a second control means which comprises the first member 77,pivot 89 and second member or inner plate 88.

Largely for convenience in illustration, the inner plate member 88 isillustrated as being generally in the shape of a sector of a circlehaving an arcuate outer margin Z of radius equal to the distance betweenpivot 76 and pivot 89. Instead, however, of actually rolling the arcuatemargin Z on the vertical line Y--Y, which is a line normal to thegrinding disk at the point of contact of the lens therewith, Fig. 4, togenerate an involute in a manner which may now be perceived to beslightly similar to that disclosed in my above mentioned Patent No.2,112,836, I simulate the rolling movement by lowering the entire innerjig E in synchronism with the pivoting of the plate 88 upwardly aboutthe pivot 89, or the reverse.

The radius RX of fore-aft oscillation about pivots 75, 75 will thus bedecreased, each time the plate 88 is raised slightly by the ratchet 63to expose a new portion of the lens to the grinding disk 16. Theintermediate portion of the lens thus will be composed of a very largenumber of transversely extending arcs, as with the constant radius upperportion of the lens. Each arc will be of constant radius across thewidth of the lens but of different radius from adjacent transverse arcs.With the inner jig illustrated, the radii of the successive arcs willvary as the involute of a circle of radius equal to the perpendiculardistance between pivot 89 and the normal contact lines Y-Y of the lensand the grinding wheel. In other words the contour of the lens in theplane of Figure 4 will be an involute curve.

It will be understood by those skilled in the art that the radius ofcurvature at any point in the intermediate portion of the lens or otherobject in the horizontal or transverse direction will be substantiallyequal to the radius of curvature in the vertical or longitudinaldirection, so that each arc will be substantially spherical in contour.It will be further understood that adjacent arcs will be substantiallytangent to each other on a meridian (in Figure 9, PU would be designatedthe principal vertical meridian) common to all arcs, The height of eacharc is determined by its intersection with the two adjacent arcs.

The final constant radius lower portion of the lens may be ground byplacing the outer ratchets 67 and 69 and the left-hand inner ratchet 63in neutral, removing bar 62 and adjusting inner ratchet 59 to lowerplate members 77 about pivot 76.

The first outer members 77 are thus operative to confine the path oftravel of the carrier 31-94 for the lens or other object for generatinga first curvature of the object in the longitudinal direction and thesecond inner member 88 is operative to confine the path of travel of thecarrier for generating a second curvature of the object in thelongitudinal direction, the first curvature being in the presentinstance a circular arc and the second curvature being an involute arc.

Further the machine will grind these different curvatures during asingle grinding operation.

In Figure 7 I have shown a polishing wheel for threaded insertion ontothe revolving and rotating plane tary shaft 17 of the machine of Figurel. The wheel comprises a piece of flexible material such as felt, a,clamped between two rings, b, which are secured to the bowl-like member,c, by means of screws, d. The tension in the flexible material may beadjusted by means of the screws, d.

The ring, e, the lower edge of which is approximately shaped to thecontour of the lens 97 ground by the machine of Figure 1, prevents theedge of the lens from being rounded off during polishing operation andis secured by screws, f, to the lens block 94.

The bowl-like member, 0, is supported above the bearing casting 12 sothat is free to revolve and rotate in a manner similar to grinding wheel16, in Figure l, the protective guard 20 having been removed from thecasting 12. The jig A is preferably operated during polishing toregenerate the lens surface, and thus improved contact between thepolishing surface and all points on the lens surface is obtained.

Referring now to Figures 8, 9 and 10, a modification of the grinding jigmechanism A, shown in Figures 1 to 6 is illustrated.

In the embodiment shown in Figure 8, instead of oscillating the carriageabout an axis which is parallel to the grinding surface of the grindingwheel, the axis of oscillation of the carriage extend obliquely to thesurface of the grinding wheel. Further, instead of generating aninvolute of a circular arc, the inner jig assembly of the presentembodiment is adapted to generate an involute of an involute curve. Ithas been found that the dioptric power of a lens having a contour whichis an involute of an involute will have a more uniform rate of change.

The ratchet mechanism for raising and lowering the inner jig assembly Eand the drive therefor may be the same as that shown in Figure 1. Outerratchet screws 100 are connected to first control means or carriagemounting means comprising bearing members or hearing blocks 101 and 102which are vertically slidable in spaced pairs of uprights 43' inguideways defined by normal movement mounting means comprising plates103. Carriage 104 comprising side bars 105 is pivotally mounted in thebearing blocks or members 101 by means of tubular shafts 106 carried bythe carriage mounting arms 107 and 107'. The carriage 104 is thusmounted for oscillation about an obliquely extending axis T-T.

For driving the inner ratchet mechanisms which are identical with thoseof Figure 1 and have, therefore, been given the same reference numerals,a rod 109 extends through the lower right hand bearing block 102 and isactuated in a manner entirely similar to the actuation of the rod 52 inFigure 1. Reciprocation of the rod 109 in the manner shown in Figure lpivots a crank 110 about a pin 111 carried by the bearing block 102. Anextension 112 of the crank 110 is connected to a rod 114 extendingthrough the tubular shaft 106 of the carriage mounting arm 107. Theinner ratchet mechanism is thus operated in a manner similar to thatshown in Figure l in spite of oscillation of the carriage 104 on theaxis TT and in spite of vertical reciprocation of the carriage by meansof the ratchet screws 100. Reciprocation of the rod 114 along the axisof oscillation, TT, rocks the shaft 115 pivotally mounted by thecarriage 104 due to a rigid connection between the shaft 115 and the arm116 which is pivotally connected to the rod 114. A wire biasing spring113 bears against the carriage mounting arm 107 and the arm 116 to biasthe arm 116 in the counterclockwise direction to bias the actuating rod109 outwardly away from the upright 43'. Rocking movement of the shaft115 is transmitted to extension 58 of the ratchet 59 by means of avertically extending arm 120 to actuate the inner ratchet mechanism inthe same manner as in Figure l. The extension 121 serves to balance thecarriage 104 in its oscillation about the axis TT.

Instead of operating the carriage by means of a universal connection tothe lens carrier assembly as in Figures 1 to 7, an adjustable hanger bar123 depends from the cross bars 105 of the carriage for univeralconnection at its lower end with an actuating rod similar to the rod 30in Figure 2. The actuating rod is adjusted to swing the carriage morethan is necessary in the lowest to the carriage.

position of'the carriage. so that in the highest position of thecarriage an adequate swing will still be imparted The universal jointconnection is indicated at 124. The first moving means thus compriseshanger bar 123 and universal joint 124.

Instead of a pivotally mounted inner plate member for generating aninvolute of a circular arc, a second or involute member comprising aninner plate member 125 is provided which is mounted forsimulated'rolling movement to generate an involute of an involute. Tothis end, an outer margin Z of the inner plate member 125 adjacent thepivot 76, defines an involute curve. This involute margin Z isconstrained to simulate rolling on the axis Y'-Y' normal to the grindingwheel surface.

In the present instance the constraining means or second member mountingmeans comprise a roller 127, rotatably mounted by the crossbars 105which is tangent to the vertical line Y'Y', an opposing roller 129,guide block or constraining member 130 and spring 131. The spring 131 ismounted by means of a bolt 132extending through the end of the platemember 125 through an aperture therein which is designed to affordadequate clearance for rocking of the plate member. The bolt 131 issecured in the constraining block 139. It will be observed that themargin 133 of the plate member 125, which faces the constraining block130, is arcuate and may be of such curvature as to tend to promote theaccuracy of simulated rolling of the plate member 125. Specifically, thecurvature of the margin 133 is such that for a perfectly simulatedinvolute, the margin 133 will perfectly accommodate the proper movementof. the end portion of the plate member 125. Movement of the lens in theradial direction is thus under the control of a second control meanscomprising first member 77, constraining member 130 and second member125.

The same may be true of the margin 135 contacting the roller 129. If themargins 133 and 135 are properly designed, there need be no loosenessbetween the constraining member and the plate 125 duringthe generationof the curve.

The plate member 125 is thus so constrained that, for example, upon theintermittent raising of the flexible strap 87 secured to the involutemargin Z, the constraining members will ideally retain contact with theplate, member 125' and constrain it to simulate an involute curve. Thespring 131 is of sufficient size to substantially resist movement of theplate 125 downwardly under-thesurging of the counterbalance such as93-shown in Figure 1 which is connected to the opening 137 in the plate125.

The operation of the embodiment of Figure -8 is,similar to that ofFigure 1. During grinding of a constant radius portion of the lens, theconnecting bar 62 is removed andthe-ratchet mechanism 59 raises orlowers the outer plates'77, the inner plate 125 and lens carrierassembly moving therewith. For example, the ratchet mechanism 59 mayraise the plates 77 one-thousandth of an inch for each half oscillationof the carriage 104 on the axis TT. If it is now desired to generate aninvolute of'an involute+-namely, the involute of the margin Z of theplate member 125, the connecting bar 62 is connected and the ratchetmechanism 63 is energized to raise the'plate 125 while the entire innerjig assembly E is lowered by means of the ratchet screws 100.

It will be observed that the machine of the present invention generatesa series of minutely or infinitesimally narrow, substantially sphericalsegments of gradually varying diameter, the spherical center of allsegments lying in the same plane, each segment being tangent to adjacentsegments on a common meridian lying in this plane-(e. g. meridian PU inFigure 9), and the area of each segment being determined by itsnatural-intersec tion. with the adjacent spherical segments.Certainlines of natural intersection Q, R, S, T, are shown in Figure;

1.0, for, example. illustrated in Figure 1', the segmentsare-generatedrabout. an axis parallel to the surface of the grindingwheeliand in the embodiment of Figure 8, the segmentsare generated aboutan axis sloping with respect to the surface of the wheel.

In Figure 9 is illustrated the principle'of the genera:- tion of aninvolute of an involute. For example, if the curve X1, X2, X3, X4, is aninvolute correspondingjto the'involute margin Z' and the line XIQ isconsidered toi represent a stringto be wrapped onto the involute curve:

X1, X2, etc., it will be observed that the arc QRST is generated, theline X2R extending tangentto the involute curve X1X4-at point X2, theline X3S" extending tangent to the curve X1X4 at point X3 and thelineX'4T. ex; tendingtangent to the involute curve at point X4. The areQRST is part of the principal vertical longitudinal. meridian PU shownin Figures 9 andv l0'and corresponds to the contour of the lens seen inelevation in Figure 8.

Figure 10 illustrates certain lines of natural intersec-. tion (Q, R, S,Tlbetween adjacent segments generated; by the machine of Figure 8.Figure 11 illustratescorresponding lines (Q, R, S, T) in a lensgenerated by the. machine of Figure 1. It will be observed that thelines Q, R, S, T in Figure 10 define a reading area which is somewhatmore ample as measured-for example on the principallong-itudinalmeridian from U to T, than the reading area-140" of the lens of Figure11. The corner. portions141 of the distance area 142 are also moreamplethan portions 141 of the distance area 142 of Figure 11 and thusprovide better distance vision. Further, th'ere'is less-distortion inthe intermediate dioptric curvature portion 143*than in thecorresponding portion 143. It has been found. in practice that lensesproduced by the machine of Figure 8 are superior to those produced bythe:

machine of Figure l-in these respects.

It will further be observed that the lens shown in F-ig-y ure 10 istheoretically generated in one direction by a generating-line extendingfrom a particular-point in'the' principal meridian such as Q to the axisTT and at right angle to the axis. Thisgenerating line is then oscillated on the axis TT. The transverse generating line such as QV extendsobliquely to the radius of curvature line QX1 of the principallongitudinal meridian PU at the point Q. It will be observedthattransverse generat ing' axis TT intersects the'radius of curvature lineQXl' at the end'ofthe radiuscurvature lineXl', at-the time ofs'tartinggeneration of atheoretical segment Q;

While generation of convex lens surfaces have been described, concavelens surfaces could also be generated by the use of "a suitable grindingsurface, such as a spherical grindingsurface andwith other suitableadjustments of:

the jig-mechanism. Also, parabolic or cylindrical lenses could'begenerated by a suitable adjustment of th'e jig mechanism. For example,to generate a cylindrical lens,

pivot 76 could be raised or lowered in Figure 4' relative to the axisofoscillation in which case the new lens would be oscillated about the newaxis and would be rotated transversely about point 76. The invention isnot limited to-len'ses, since dies for plastic lenses could be'formed'by means of'the apparatus of'my invention.

Inmy Patent No. 2,112,836, above mentioned, apair of radius arms ofdifferent lengths were swung around fixed points'tocontrol thecurvature'transversely. The segments thus generated could not bespherical throughoutsince the action of the radius arms introduces aslight error. However the machines of the present invention are suchthat a succession of substantially spherical sur-" faces of graduallyvarying diameter are ground. and the lenses produced bythe machines ofthe present invention. are more, nearlytheoretically perfect thanthelenses producedby the machines of my former-patent, especially at theouter margins.

It will:'bezunderstood that modifications and variations In theembodiment of the: machine.

may be effected Without departing from the scope of the novel conceptsof the present invention.

I claim as my invention:

1. In a grinding machine for operation in conjunction with a grindingmember, a movable support, a carrier for the object to be ground carriedby said support, first moving means for moving said support and carrierin a first direction across the grinding member, first control means forcontrolling the path of travel of said carrier in said first directionfor determining the curvature of the object in said first direction,second moving means for moving said carrier into operative relation withthe grinding member in a second direction transversely of said firstdirection of movement, and second control means for confining the pathof travel of the carrier for determining the curvature of the object insaid second direction, said last mentioned control means comprising afirst member operatively mounted on said movable support for confiningthe path of travel of said carrier for generating a first curvature ofthe object in said second direction, and a second member operativelymounted on said first mem ber for confining the path of travel of saidcarrier for generating a second curvature of the object in said seconddirection.

2. In a grinding machine, the combination with a grinding wheel having agenerally plane grinding surface of a carriage, normal movement mountingmeans mounting said carriage for movement generally normal to thegrinding surface, first control means mounting said carriage formovement to generate a curvature in a first direction, a first memberpivotally carried by said carriage for generating a first curvature in asecond direction transverse to said first direction and a second membercarried by said first member for movement to generate in conjunctionwith the movement of said carrier along said normal movement mountingmeans a second curvature in said second direction.

3. In a grinding machine, the combination with a grinding wheel having agenerally plane grinding surface of a carriage, normal movement mountingmeans mounting said carriage for movement generally normal to thegrinding surface, first control means mounting said carriage formovement to generate a curvature in a first direction, a first membercarried by said carriage for generating a first curvature in a seconddirection transverse to said first direction and a second member carriedby said first member for movement to generate in conjunction with themovement of said carrier along said normal movement mounting means asecond curvature in said second direction.

4. In a grinding machine, the combination with a grinding wheel having agenerally plane grinding surface of a carriage, normal movement mountingmeans mounting said carriage for movement generally normal to thegrinding surface, first control means mounting said carriage foroscillation in a first direction about an axis extending in a directiontransverse thereto, a first member carried by said carriage forgenerating a first curvature in a second direction transverse to saidfirst direction and a second member carried by said first member formovement to generate in conjunction with the movement of said carrieralong said normal movement mounting means a second curvature in saidsecond direction.

5. In a grinding machine, the combination with a grinding wheel having agenerally plane grinding surface of a carriage, normal movement mountingmeans mounting said carriage for reciprocating movement in a directiongenerally normal to the grinding surface, first control means mountingsaid carriage for oscillation about an axis, a first member, first pivotmeans mounting said first member on said carriage for pivotal movementon an axis intersecting said axis of oscillation, a second membercarried by said first member, normal moving means for moving saidcarriage normal to the grinding surface, and second member moving meansfor moving said second member in synchronization with said normal movingmeans.

6. In a grinding machine, the combination with a grinding wheel having agenerally plane grinding surface of a pair of spaced frame membersextending generally normally to said grinding surface, bearing memberscarried by said frame members for movement parallel to said framemembers, a carriage pivotally carried by said bearing members foroscillation about a first axis, a first member carried by said carriagefor pivotal movement on a second axis intersecting said first axis ofoscillation, and a second member carried by said first member formovement in a locus of planes substantially intersecting said first axisof oscillation.

7. In a grinding machine, the combination with a grinding wheel having agenerally plane grinding surface of a pair of spaced frame membersextending generally normally to said grinding surface, bearing memberscarried by said frame members for movement parallel to said framemembers, a carriage pivotally carried by said bearing members foroscillation about a first axis, a first member carried by said carriagefor pivotal movement on a second axis intersecting said first axis ofoscillation, a second member carried by said first member for movementin a locus of planes substantially intersecting said first axis ofoscillation, bearing member moving means for jointly moving said bearingmembers general- 13 normally to said grinding surface, and second membermoving means for moving said second member in synchronism with saidbearing member moving means.

8. In a grinding machine, the combination with a grinding wheel having agenerally plane grinding surface of a pair of spaced frame membersextending generally normally to said grinding surface, bearing memberscarried by said frame members for movement parallel to said framemembers, a carriage pivotally carried by said bearing members foroscillation about a first axis, a first member carried by said carriagefor pivotal movement on a second axis intersecting said first axisof'oscillation, a second member carried by said first member formovement in a locus of planes substantially intersecting said first axisof oscillation, first moving means for oscillating said carriage on saidfirst axis, and first member moving means for moving said first memberin synchronization therewith.

9. In a grinding machine, the combination with a grinding wheel having agenerally plane grinding surface of a pair of spaced frame membersextending generally normally to said grinding surface, bearing memberscarried by said frame members for movement parallel to said framemembers, a carriage pivotally carried by said hearing members foroscillation about a first axis, a first member carried by said carriagefor pivotal movement on a second axis intersecting said first axis ofoscillation, a second member carried by said first member for movementin a locus of planes substantially intersecting said first axis ofoscillation, first reversible ratchet means carried by said framemembers for moving said bearing members generally normally to saidgrinding surface, second reversible ratchet means carried by saidcarriage for pivoting said first member on said second axis, andreversible ratchet means carried by said first member for movement ofsaid second member in synchronization with movement of said bearingmembers.

10. In a grinding machine, the combination with a grinding wheel havinga generally plane grinding surface of a pair of spaced frame membersextending generally normally to said grinding surface, bearing memberscarried by said frame members for movement parallel to said framemembers, a carriage pivotally carried by said bearing members foroscillation about a first axis, a first member carried by said carriagefor pivotal movement on a second axis intersecting said first axis ofoscillation, a second member carried by said first member for movementin a locus of planes substantially intersecting said first axis ofoscillation, first reversible ratchet means carried by said framemembers for moving said bearing members generally normally to saidgrinding surface, second reversible ratchet means carried by saidcarriage for pivoting said first member on said second axis, reversibleratchet means carried by said first member for movement of said secondmember in synchronization with movement of said bearing members, andcrank means for oscillating said carriage in synchronization selectivelywith said first and third ratchet means or with said second ratchetmeans.

11. In a grinding machine, the combination with a grinding Wheel havinga generally plane grinding surface of a pair of spaced frame membersextending generally normally to said grinding surface, bearing memberscarried by said frame members for movement parallel to said framemembers, a carriage spanning between and pivotally carried by saidbearing members for oscillation about a first axis, a first membercarried by said carriage for pivotai movement on a second axisintersecting said first axis of oscillation, and first pivot meanscarried by said carriage for controlling pivoting of said first memberabout said second axis.

12. In a grinding machine, the combination with a grinding wheel havinga generally plane grinding surface of a pair of spaced frame membersextending generally normally to said grinding surface, bearing memberscarried by said frame members for movement parallel to said framemembers, a carriage pivotally carried by said bearing members foroscillation about an axis, an involute generating member carried by saidcarriage for movement in a locus of planes substantially intersectingsaid axis of oscillation, bearing member moving means for moving saidbearing members parallel to said frame members, and involute membermoving means for moving said involute member in synchronization withsaid bearing member moving means.

13. In a grinding machine jig mechanism for generating an involutecurve, a frame, a carriage carried by said frame for movement in onedirection, an involute generating member carried by said carriage forarcuate movement having at least a component in a direction opposite tosaid one direction, carriage moving means for moving said carriage insaid one direction, and involute member moving means for moving saidmember in synchronization with said carriage but with the member havingat least a component of movement in a direction opposite to said onedirection to move the member as a function of an involute curve.

14. In a grinding machine jig mechanism for generating an involutecurve, a frame, a carriage carried by said frame for movement in onedirection, an involute generating member carried by said carriage andhaving an arcuate margin of curvature to generate said involute curve,constraining means including a constraining member constraining saidmember for arcuate movement having a component in a direction oppositeto said one direction to bring successive points on said arcuate margininto opposition to said constraining member, carriage moving means formoving said carriage in said one direction, and involute member movingmeans for moving said involute generating member in synchronization withsaid carriage but with the member having a component of movement in adirection opposite to said one direction, the arcuate movement of saidinvolute generating member defining an involute curve.

15. In a grinding machine jig mechanism for generating an involute of acircular arc, a frame, a carriage carried by said frame for linearmovement in one direction, an involute generating member carried by saidcarriage for pivotal movement having a component in a direction oppositeto said one direction, carriage moving means for moving said carriage insaid one direction, and involute member moving means for pivoting saidmember in synchronization with movement of said carriageby-saidcarriagemovingmeans but with the. mem+ her having a component, of movement in adirection opposite to said one direction to move said member as afunction of an involute of a circular are.

16. The grinding machine of claim. 14 wherein said arcuate margin has aninvolute curvature andthe arcuate movement of said involute generatingmember defines an involute of the involute curvature of said arcuatemargin.

17. The grinding machine of claim 4 wherein said carriage mounting meansmounts saidcarriage for oscillation about an axis that is at aninclination to said plane grinding surface.

18. In a grinding machine, a carrier for an object to be ground, firstmoving means for oscillating said-carrier arcuately about a given axis,involute mounting means constraining said carrier for arcuate movementradially relative to said axis in accordance with a predeterminedfunction, involute moving means for actuating said carrier to movethrough successive increments of said last mentioned arcuate movementradially of said axis, and linear moving means for linearly moving saidcarrier in successive increments in a direction generally. opposite tothe'last mentioned arcuate movement and in timed.

relation to said first and second mentioned increments of arcuatemovement of said carrier under the control of said first moving meansand said involute moving means to progressively vary the radius on whichsaid carrier is moved 1 about said axis in accordance-with an involuteof said'predetermined function.

19. In a grinding machine, a carrier for an object to be ground, firstmoving means for cyclically movingsaid carrier transversely on acircular are about a given axis, involute mounting means constrainingsaid carrier for movement in a radial direction relative to said axis inaccordance with a predetermined function, and involute moving means foractuating said carrier to move radially of said axis in successiveincrements in timed relation to the cyclical transverse movement of saidcarrier about said axis to generate a surface composed of successivetransverse arcs of radii progressively varying in accordance with saidpredetermined function.

20. In a grinding machine, a carriage, first control means mounting saidcarriage for arcuate movement about a given axis, an involute generatingmember carried by said carriage and pivotal relative thereto, a carrierfor an object to be ground carried by said involute member, involutemember moving means for progressively moving said involute member aboutits pivot as the involute member moves about said axis, and carriagemoving means for progressively shifting said axis in timed relation tothe progressive movement of said second member about its pivot but in anopposite general direction to generate a surface having an involutecurvature.

21. In a grinding machine, a carriage, carriage mounting means mountingsaid carriage for arcuate movement about a given axis, an involutemember carried by said carriage and constrained for rocking movementrelative 'to a surface carried by said carriage, involute member movingmeans for progressively moving said member under the constraint of saidsurface carried by said carriage, and carriage moving means forprogressively shifting said axis in timed relation to the progressivemovement of said involute member by said involute member moving meansbut in an opposite general direction to generate a surface having aninvolute of the curvature defined by the rocking movement of saidinvolute member.

22. In a grinding machine having a generally planar grinding surface, acarrier for an object to be ground, a carriage supporting said carrier,carriage mounting means mounting said carriage for arcuate oscillationon a given axis, first moving means for oscillating said carriage onsaid axis to oscillate said carrier back and forth across said grindingsurface in a first direction, an involute generating member carried bysaid carriage for oscillation therewith and carrying said carrier,involute member mounting means constraining said invoiute generatingmember for arcuate movement having a radial component relative to saidaxis and having a normal component relative to said grinding surface,involute mem- 'ber moving means connected to said involute generatingmember .and operative to move said involu-te generating memberstep-by-step through successive increments under the constraint of saidinvolu'te member mounting means, normal movement mounting means mountingsaid carriage mounting means for movement normal to said grindingsurface, linear moving means connected to said carriage mounting meansand operative to move said carriage mounting means along said normalmovement mounting means to move said carriage step-by-step in adirection normal to said grinding surface, said linear moving meansbeing synchronized with said involute member moving means and said firstmoving means to move said carriage normal to said grinding surface a 2step in one sense when said involute member moving means moves saidinvolute member a step having a component normal to said grindingsurface but in the opposite sense and when said first moving meansoscillates the carriage to an extreme position about said axis with theobject to be ground out of engagement with said grinding surface, andpower means for energizing said first moving means, said linear movingmeans and said involute member moving means to generate a surface onsaid object whose curvature varies as an involute function.

23. A method of forming a surface with a gradually varying curvature,which comprises relatively moving an object to be ground transverselyacross a grinding surface about a first radius to form a firsttransverse are on said object of given radius of curvature, minutelyshifting said object arcuately in a direction having a componentparallel to the longitudinal axis of the object and having a componentnormal to the grinding surface, and linearly moving the object in adirection normal to the grinding surface and moving the object acrossthe grinding surface about a slightly diiferent radius to form a secondtransverse are on said object of slightly different radius of curvature,repeating the transverse moving and longitudinally shifting steps togenerate an involute curvature on the object along the longitudinal axisthereof, and controlling the longitudinal shifting of the object inrelation to the successive transverse radii of curvature so that eachtransverse segment in the surface generated on said object will have asubstantially fragmental spherical contour.

References Cited in the file of this patent UNITED STATES PATENTS Re.14,751 Brockbank Nov. 18, 1919 729,781 Mundorff June 2, 1903 977,268Bucs'ko Nov. 29, 1910 1,343,050 Goodwin June 8, 1920 1,458,623 KnowlesJune 12, 1923 1,699,045 Butler Jan. 15, 1929 1,827,748 Holman Oct. 20,1931 1,836,542 Miller Dec. 15, 1931 1,869,461 Bugbee Aug. 2, 19321,922,912 Fox Aug. 15, 1933 1,928,196 Betrancourt Sept. 26, 19332,016,134 Culver Oct. 1, 1935 2,278,314 Houchin Mar. 31, 1942 2,403,659Hayward a- July 9, 1946 2,482,698 Tillyer Sept. 20, 1949 FOREIGN PATENTS808,198 Germany July 12, 1951

